Apparatus for reduction of frangible material



June 1952 G. w. BORTON ETAL 2,600,964

APPARATUS FOR REDUCTION OF FRANGIBLE MATERIAL Original Filed Aug. 9, 1946 5 Sheets-Sheet l FIG. 5.

A TTORNE).

June 1952 5. w. BORTON ETAL APPARATUS FOR REDUCTION OF FRANGIBLE MATERIAL 3 Sheets-Sheet 2 Original Filed Aug. 9, 1946 A 770R NE)- June 1952 G. w. BORTON ETAL APPARATUS FOR REDUCTION OF FRANGIBLE MATERIAL 3 Sheets-Sheet 5 Original Filed Aug. 9, 1946 DRUM AND Rom thr ATTORNEX Patented June 17, 1952 APPARATUS FOR REDUCTION OF FRANGIBLE MATERIAL George W. Burton, Philadelphia, and Stanley D.

Hartshorn, Wayne, Pa., assignors to Pennsylvania Crusher Company, Philadelphia, Pa., a corporation of New York Original application August 9, 1946, Serial No. 689,872. Divided and this application April 1, 1948, Serial N0. 18,368

3 Claims.

This invention relates to the manufacture of plastics and more particularly to the production of uniform moldable plastic particles.

It is an object of this invention to provide apparatus for the reduction of frangible pieces to small particles preserving the desired form of the fractured pieces by effective impact and screening in a continuous manner subjecting all particles to similar milling action.

A further object of the invention is to provide a horizontal axis impact mill with rotary hammers and lifting shelves within a cylindrical screen cooperating to give the desired fracturing action on material such as pieces of previously specially polymerized plastic.

Other and further objects will appear from the following description taken together with the figures in which:

Fig. 1 is a side view of apparatus for preparing and reducing a polymerizable substance;

Fig. 2 is a vertical longitudinal sectional view of a Bradmill;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 2;

Fig. 4 is a perspective view of a particle after breaking the polymerizable substance in the sawtooth crusher of Fig. 1 and before reduction in the Bradmill of Fig. 2; and

Fig. 5 is a perspective View of a typical particle after reduction.

In general, this invention relates to the preparation of a polymerizable material in which a. partially polymerized material is rapidly reduced to particles to maintain a homogeneity of polymerization.

Referring to Fig. 1, a vat I is shown in which is placed a plastic such as a phenol-formaldehyde condensation product. When passed into the vat I this plastic has been processed to the point where it is soft when heated and hard when cooled and is homogeneously in a stage of partial polymerization. The plastic mass is maintained in a heated, and plastic, homogeneous condition in the vat I and is fed in this condition from the vat I into the heated rolls 2 where it is compresed into a strip 3 approximately 4" in thickness. By attenuating the plastic mass into a thin strip it can be cooled rapidly. This rapid cooling is important in bringing about a uniform decrease in the rate of polymerization which is reduced upon the cooling of the plastic. As the strip-is cooled almost instantaneously upon leaving the rolls 2, and the rate of polymerization correspondingly affected, the polymerization of all portions of the strip 3 is substantially homogeneous and a stiff strip of homogeneously, partially polymerized plastic is obtained. The brittle strip 3 is subsequently fed into a saw-tooth crusher 4 which chops the pieces 3 up into pieces 5 of approximately to 1 /2" in width or length and A in thickness. A typical chip 5 formed by breaking the strip 3 in the crusher 4 is shown in Fig. 4.

The chips 5 fall from the saw-tooth crusher 4 onto a continuous belt 6 which carries them to the Bradmill crusher I. The Bradmill crusher I shown in Fig. 2 is comprised of a drum 8 rotating on a horizontal axis in a casing 9. The term Bradmill is the trade-mark of the Pennsylvania Crusher Company applied to their crushing machines having a rotary drum lifting the material and dropping it into the path of rotary hammers within the drum.

Fig. 3 is a radial section of the Bradmill showing the drum 8 rotating counterclockwise and having a screen II around its perimeter perforated with perforations ID to permit passage of particles I5 of the order of 10 mesh sieve size. The shelves I2, I3 and I4 are positioned in the drum 8 having impact surfaces forming angles of 20 degrees to 35 degrees with the radium of the drum 8.

A hammer carrying rotor assembly I8 rotates counterclockwise coaxially with drum 8 and carries hammers I9 for striking the polymerizable material with surfaces 2|. The chips 5 when struck by the fast-moving surfaces 2| are fractured by the impact and thrust against the surfaces I6 of the shelve I2, I3 and I4. Th resulting particles I5 suffer further fracturing by the second impact and either fall to the screen I I or continue to be struck by impact surfaces It and El until they fall to the screen II. The shelves I3 and I l alternate with the shelves I2 and in every succession of four shelves there is one shelf I3 and one shelf HI separated by a shelf I2. The carrying surfaces ll of the shelves I4 extend to and are contiguous with the screen II while the carrying surfaces ll of the shelves I3 extend toward but are spaced away from the screen II. The shelves I2 having no carrying surfaces are spaced further away from the screen II than the carrying surfaces Il. The particles I5 on the screen II are therefore free to slide under the shelves I2 and I3 and catching on the surfaces I! are carried upward with the rotation of the drum 8. In the sliding action of the fractured particles on the moving screen II the particles are tumbled over each other and those less than a predetermined size set by the perforations l pass through the perforations I0 and into the casing 9 from which they fall through a discharge opening 22. The particles greater than the predetermined size and too large for passage through the perforations l0 are carried upward on the surfaces ll by the rotation of the drum and at the top of the cycle drop off into the path of the hammer surfaces 2| and are subjected to further fracturing by impact. This process is repeated until the particles are reduced to such size as will pass through the per forations Ill. The carrying surfaces ll of the shelves |3 while not extending to the screen so as to carry large particles serve to limit the quantity of particles sliding to the shelf M by holding up any pile of particles that may build upon the screen.

As shown in Fig. 2, the hammers H) are hung on bars 23 inserted in plates '24 fastened together on a shaft 26 by collars 21 to form a rotor assembly l8. On the end of shaft 26 is provided an L-shaped member which forms a rigid hammer 28 having impact surfaces 29. This hammer 28 and its surfaces 29 cooperate with the hammers |9 and the surfaces 2| to fracture the particles 5.

The chips are fed into the drum 8 through a chute 3| formed in one side of the casing 9. The drum 8 and the shaft 26 are driven through an opening in the side of casing 9 opposite chute 3|. A pair of pulley blocks 32 support a rotatable quill 33 which carries the drum 8 on a flanged end 34 extending into the casing 9. The quill 33 is turned by sprocket 36 driven by suitable means. The shaft 26 is carried inside the quill 33 on bearings 31 and the shaft is driven by a pulley 38 powered by suitable means.

The process operates as follows: A polymerizable substance such as phenol-formaldehyde condensation compound which has been prepared and has polymerized into a plastic mass when heated is placed in the vat This mass continues to polymerize in the vat and would eventually assume a hard and infusible nature.

While the mass in the vat is in the plastic when hot but stiff when cool state, it is fed out of the vat 1 through heated rolls 2 which compress the mass into a thin wide strip of approximately thickness. This thin strip 3 is rapidly and evenly cooled because of its thinness and the rate of polymerization which is substantially lowered by the decrease in temperature is uniformly reduced for all parts of the strip as it leaves the rolls 2. The homogeneity of the partial polymerization thus attained in the material strip 3 is preserved by rapidly reducing the plastic to particles l5 of uniform size in which size the further polymerization of the plastic is uniform. To obtain this reduction the hardened strip is immediately cracked up in the saw-tooth crusher 4 and the particles 5 of plastic material from the crusher 4 drop onto a continuous belt 6 and are carried down to chute 3| of the Bradmill The particles 5 dropping into the chute 3| slide into the rotating drum 8 and are picked up on the shelves |'2, I3 and M by the rotation and carried upward to the top of the cycle from which they are dropped into the path of the rapidly rotating rotor I8 and struck by the hammer Surfaces 2| to be fractured by impact. After bouncing off the impact surfaces 2| and Hi, as before mentioned, the fractured particles i5 collect on the screen II and sliding over the screen upon rotation of the drum 8 the smaller particles fall through the perforation and out into casing 9 thence through discharge opening 22. As before mentioned, those over-size particles too large to pass through the perforations ID are carried upward by the rotation of drum 8 for a repetition of the fracturing procedure.

It is desired to remove the particles l5 from the Bradmill I as soon as they have been reduced to the proper size for passage through screen II. It is also necessary to reprocess those oversize particles which have not been sufliciently reduced. To separate the two sizes the mixture of particles |5 that falls on the screen slides over the screen II as the drum 8 rotates. This sliding tumbles and tosses the loose particles IE on the rotating surface of screen so that the 10-mesh sieve particles are given an opportunity to drop through the perforations |0 before being carried upward and unnecessarily reprocessed. The carrying surface I! of theshelf l3 assists in obtaining a good mixing of the various sized particles by leveling off the particles that have fallen onto the screen I and preventing a pile-up which would trap the under-size particles away from the screen.

By this process a particle of the strip 3 is broken, fractured, sorted and passed out for further processing in a short time. A particle is reduced to a desired size quickly to prevent any more polymerization of large particles than is necessary. This is important as uneven polymerization decreases with the size of the individual particle of polymerizable plastic. In small polymerizable particles the condensation process is essentially equal in all parts of the particle and equivalent sizes of polymerizable particles under equivalent conditions have equivalent rates of polymerization. Therefore, the preservation and creation of homogeneity in the polymerization of a condensation product or other polymerizable plastic is aided by reducing the plastic to particles in which the rate of polymerization will be substantially the same for all parts of the material in all the particles.

This process achieves the preservation of homogeneity of the polymerization by minimizing the period during which the polymerizable material is formed in large pieces and by reducing it to small particles as rapidly as possible. This process also has the advantage of subjecting the polymerizable material tofracturing only to the extent that is necessary for attaining the desired small particle by removing the small particle from the fracturing device as soon as it has achieved the desired smallness. The final product has a very small percentage of dust due to the perpetual alternate screening and crushing so that the finer particles are screened out as soon as they are produced. The rate of pour, for instance, through a funnel orifice, is excellent as is the weight per cubic centimeter, the size of the particles being graduated and averaged to very compactly fill in the intervening spaces.

Various modifications of the apparatus involved may be resorted to within the scope of this invention. For instance, the saw-tooth crusher 4 may be of the single roll type and the times of treatment will be regulated according to the characteristics of the material. After the preliminary polymerization the material is cooled and kept below a temperature at which there is any substantial polymerization so that the final crushing may be timed at any convenient interval. The invention is not intended to be restricted to the specific embodiments shown but is intended to cover such modifications thereof as fall within the appended claims.

This is a division of our application Serial No. 689,372, filed August 9, 1946, now Patent No. 2,516,295 of July 25, 1950.

What is claimed is:

1. Apparatus for reduction of pieces of thin frangible material comprising a horizontal rotary cylindrical screen adapted to discharge outwardly particles less than a predetermined size, impact members rotating around an axis within said screen receiving and fracturing said pieces of thin frangible material and delivering them to said screen, inwardly directed shelves abutting the inner surface of said screen and adapted to pick up over-size particles and return them to said impact members for further fracturing and separate strips between said shelves, each strip being spaced from said screen and positioned at an angle to the radius of said axis to interpose surfaces receiving the impact of material from said rotating members and deliver said material outward to said screen between said shelves.

2. Apparatus for reduction of pieces of frangible material comprising a horizontal rotary cylindrical screen adapted to discharge downwardly particles less than a predetermined size, impact members rotating around an axis within said screen receiving and fracturing said pieces of frangible material and delivering them to said screen, inwardly directed shelves adapted to pick up over-size particles and return them to said impact members for further fracturing and separate strips between said shelves, each strip being spaced from said screen and positioned at an angle to the radius of said axis to interpose surfaces receivin the impact of material from said rotating members and deliver said material to said screen between said shelves.

3. Apparatus for reduction of pieces of frangible material as set forth in claim 2 in which certain of said shelves are positioned to have their outer edges at the surface of said screen and intermediate strips are spaced from said screen to permit material to pass between the screen and the inner edges of said intervening shelves.

GEORGE W. BORTON. STANLEY D. HARTSHORN,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,914 Heygel Jan. 16, 1843 104,910 Whelpley June 28, 1870 301,353 Fritz July 1, 1884 910,196 Hess Jan. 19, 1909 1,713,957 Duvall May 21, 1929 1,850,824 Bennett Mar. 22, 1932 1,910,234 Boynton May 23, 1933 1,948,504 Borton Feb. 27, 1934 2,108,793 Borton Feb. 22, 1938 2,127,116 Heimberger Aug. 16, 1938 2,155,150 Schacht Apr. 18, 1939 2,199,729 Peterson May 7, 1940 2,228,351 Hartshorn Jan. 4, 1941 2,316,283 Piperoux Apr. 13, 1943 2,327,087 Austin Aug. 17, 1943 2,461,089 Smidt Feb. 8, 1949 FOREIGN PATENTS Number Country Date 104 626 Sweden Mar. 26. 1942 

